I think it’s indeed has something to do with it, reason why it is often called the building blocks of life. Although there are other factors that affect life span (based from one article that I read); it includes genes, cells, food and the environment.

As far as I'm aware, it's actually mainly related to aerobic respiration. There is some truth in that the faster the heart beat, the shorter the life. This is because the heart is pumping more oxygen around the body, to the tissues and into the cells. Aerobic respiration, as opposed to anaerobic, uses oxygen as well as a monosaccharide (glucose, galactose, fructose etc) to create adenosine triphosphate (ATP).

This does, however, cause the release of free radicals, which can damage the cell nucleus and cause cellular ageing. This happens to all cells in the body, very frequently, and this causes our bodies and the bodies of animals to gradually weaken and ultimately fail. Free radicals can also be the result of excessive UV exposure and toxins, like nicotine, tar, pesticides, pollution, and natural toxins found in our bodies and in food.

As free radicals are essentially just oxygen atoms missing an electron (cation), they can be fought with antioxidants. This is why antioxidants are good for you! Hope this helped.

Just to that, the reason that the free radicals are so damaging is because they are just unstable molecules and so they "steal" electrons from cells so that they become stable. The result is that this leaves the cells damaged and this is how ageing occurs.

the reasons why our life spans are the way they are may differ, but the reason they are at these set levels is often a result of reproductive capabilities.

Animals with few predators such as tortoises or animals on secluded islands with few or no predators such as new zealand's tuatara generally have longer life spans because they retain reproductive capability throughout their life. an opossum dies in 3 or 4 years because have so many predators that they can often only life long enough to reproduce. this is explained in 'Genome' the author escapes me but I suggest you check it out

There are no reasons for either - that is, they did not arrive by a process of logic or reasoning but by evolution. Cause and effect here are not so obvious. Can you provide more specifics in terms of scientific experimentation rather than hypothetical rationalization of existing phenomena?